Reciprocal microwave switching device using non-reciprocal components



June 18, 1963 c. BowNEss 3,094,676

RECIPROCAL MICROWAVE SWITCHING DEVICE USING NON-RECIPROCAL COMPONENTS Filed Dec. 21, 1959 2 Sheets-Sheet 1 INVENTOR C OL/N OWNESS KMM ATTORNEY June 18, 1963 c. BOWNESS 3,094,676

RECIPROCAL MICROWAVE SWITCHING DEVICE USING NON-RECIPROCAL COMPONENTS Filed Dec. 21, 1959 2 Sheets-Sheet 2 H0 INVENTOR COLIN BOWNESS BY i/ ATTORNEY United States Patent 3,094,676 RECIPROCAL MICROWAVE SWITCHING DEVICE USING NON-RECIPROCAL COMPONENTS Colin Bowness, Watertown, Mass, assignor to Raytheon Company, Lexington, Mass, a corporation of Delaware Filed Dec. 21, 1959, Ser. No. 861,132 7 Claims. (Cl. 333-7) This invention pertains generally to microwave switching devices and the like, and more particularly to ferrite microwave switching devices exhibiting a reciprocal relationship in the transmission of signals in opposite directions therethrough.

Microwave switches employing ferrite insert members are well known in the art, and such switches have been classified generally as either reciprocal or non-reciprocal. A circuit or device may be said to be reciprocal in the sense referred to herein if an output signal obtained at one port thereof in response to an input signal applied to a second port would be produced at such second port upon the application of such input signal at the first port. In so defining such reciprocal relationship, it is immaterial that, in some instances, the devices referred to herein will produce non-reciprocal ph ase rotations as between propagation in opposite directions therein. Such reciprocal relationship obtains with respect to propagation between ports, irrespective of the fact that there may be a 180 degree phase differential between the signals propagated in opposite directions.

Ferrite materials have found Wide use in microwave devices such as isolators, modulators, phase changers, circulators, switches and the like, and much of the utilization of these materials has been based upon the ability ofa ferrite insert member to modify some characteristic of a microwave signal (such as the phase or vector orientation thereof), in addition to the ability to absorb such signals. With particular reference to microwave ferrite devices which alter the electrical phase of a microwave signal propagated therethrough or which cause a degree of rotation of the electrical vector by way of a Faraday rotation,.it is often desirable to render variable the efiect that the ferrite produces in the microwave signal. For example, it is often desirable to vary the Faraday rotation'or the phase shift of such a signal between two limit points. This is particularly true in the case of microwave ferrite switches, wherein it is desired toeifect a switching action in response to an electrical control signal.

The microwave ferrite switch art makes use of the fact that the degree and sense of Faraday rotation or electrical phase shift are dependent upon, among other things, the magnitude and sense of the magnetic field applied to the ferrite member. For example, an increase in the strength of the magnetic field applied to a ferrite in a waveguide or the like increases the angle formed between the electrical vector of a signal in suchwaveguide and the fiducial vector obtained with no applied magnetic field. Reversal of the sense of the applied magneticfield brings about a reversal in the sense or direction of the electrical vector. By employing such a ferrite device between a pair of mode-sensitive terminal devices, the selective magnetic energization of the ferrite results in a corresponding changein the orientation of the electrical vector of microwave signal in the device, with propagation in one orientation proceeding through one branch, of

orthogonal thereto proceeding through another branch. The range of magnetic energization ordinarily, but not necessarily, applied to ferriteswitches is defined in some instances by the limits of zero field and magnetic satura-,.

tion, and in other instances by the limits of magnetic saturation in tWo opposite field senses or. polarities. As

the terminal device, and propagation in an orientation:

Patented June 18, 1963 'ice will be appreciated by: those skilled inthe art, a ferrite switch having zero applied magnetic field as one limit condition is subject toseveraldisadvantages. For example, where it is desired to have such a switch in thecondition associated with zero applied magnetic field, even where the normal energizing field is-actually at zero strength it sometimes happens that stray magnetic fields of sufiicient strength and-appropriate orientation findtheir way into the ferrite insert menrberof-the switch, resulting in an actual,- thoughunintended, appliedmagnetic field which energizes the switch into a condition not correspondingto that desired by zero intentional applied field. Obviously, where this switch-is-in the other intendedcondition of magnetic saturation, any stray magnetic fields present-would fail .to-alterthe condition of the switch, since the phase shift or Faraday rotationproduced bythe ferrite approaches a constant .level as the ferrite becomes magnetically saturated.

Another problem that. occurs in the useof a'ferriteswitch having zero applied magnetic field as-one of the intended or designed operational conditions is thefact that ferrite materials exhibit magnetic hysteresis, and once a ferrite. switch has-been energizedby anapplied;

magnetic field, it remainspartially magnetized even upon the removal ofsuch fields Hereagain, the switching condition which the switch is designed to provide at zero applied magnetic field does not obtain in the absence of; such applied field, since the remanent m-agntization gives the effect of a small applied magneticfield.

A further disadvantage of ferrite switches having zeroapplied magnetic field as one of the designed operating conditions arises as a result of low-fieldlosses. As is understood in the ferrite art, the relationship between insention loss and applied magnetic field exhibits a pro:

nounced peak at a substantial applied field which defines the condition of ferromagnetic resonance. Iii-addition,

frequencies. On the other hand, where the ferrite switch is subjected to a magnetic field of considerable strength (on either side ofbut avoiding the field strength corresponding to ferromagnetic resonance and the large loss associated therewith), the insertion loss is quite lowrand' may generally be easily tolerated.

An appreciation of the-foregoing. disadvantages which attend the use of a ferrite sm'tch having zero applied mag: netic field as one of its designed operating conditions appears to dictate the utilization'of-ferrite switches'in which zero applied magnetic field is notone of the operating conditions.

conditions in response to an applied magnetic field which varies between magnetic saturation in one sense or direction and saturation in the opposite sense. Suchswitches avoid the aforementioned disadvantages, but they have been characterized in the past by a lack of the reciprocalv relationship with respect to microwave signals propagated, therethrough inopposite directions. That is to say, where a signal applied to a first port of, such a switch produces a certainoutput at a second port, the application of such input signal to thegsecond port does notv produce such.

certain output signal at the first port.-

As will be appreciated by. those skilled; in the art, the applicationsv to which as low-loss reciprocal microwave ferrite switch may be put are both numerous anddm- Exemplary of ferrite switches of'this, latter type are those which switch between two desired portant. Exemplary of such applications is the microwave switch needed to connect a transmitter-receiver equipment selectively to either of a pair of transmittingreceiving antennas. In one condition of the switch it is required that the microwave signals be efficiently propagated from the transmitter-receiver switch port to a first antenna and back through the same port, while in the other operating condition of the switch the microwave signals presented to the switch at this port must be eflicientlypropagated to the second antenna and back to the same port. The prior art has failed to provide a satisfactory reciprocal microwave switch for this application, as well as for other applications having the same or similar requirements.

It is accordingly a primary object of the present invention to provide a microwave ferrite switch device or the like which is at once characterized by efficient propagation with low losses as well as by the reciprocal relationship in the transmission of microwave signals therethrough in opposite directions.

In accordance with the present invention, the above and other objects are achieved by means of a microwave ferrite switch or the like having at least one ferrite unit therein which may be magnetically energized selectively between two limits of applied magnetic field strength of opposite sign or sense, along with a corresponding numher (at least one) of ferrite unts which have a relatively fixed magnetic field applied thereto. 'In a simple example, the device includes a single switchable ferrite unit connected in series relationship with a single fixed ferrite unit. The relatively fixed magnetic energization applied to the fixed units produces a correspondingly fixed amplitude and sense of Faraday rotation or electrical phase shift, depending upon the type of device employed. The selectable switch energization which is applied to the switching unit produces, in one condition, a Faraday rotation or electrical phase shift of amplitude and sense equal to that produced by the fixed unit, and, in the other switching condition, a rotation or phase shift of equal amplitude but opposite sign.

As is understood, a microwave ferrite device, magnetized in a steadystate condition may be, in itself, a nonreciprocal device. The degree of Faraday rotation or electrical phase shift produced by such a device depends upon a plurality of factors, but the sense of such rotation or phase shift depends upon the direction alone of the applied magnetic field. The present invention achieves reciprocal propagation characteristics in a microwave ferrite device by employing paired non-reciprocal ferrite units, one of which is the switch unit which is switchable between two conditions of equal magnitude but opposite sense, and the other of which is fixed in one of these two conditions. By this pairing of non-reciprocal ferrite devices, the desired reciprocal relationship is achieved.

It will be understood that it is generally desirable in the present invention to magnetize the ferrite members to saturation. However, it should be borne in mind that saturation is not a necessary condition to the successful operation of devices formed in accordance with the teaching of this invention, since the problems of low-field loss and hysteretic remanence are avoided by the present invention even where, due to lack of complete saturation, stray fields may have some effect.

In addition, it will be appreciated that the basic concept of achieving the reciprocal relationship in bi-directional signal propagation resides in the aforementioned pairing of fixed and switched non-reciprocal ferrite units, irrespective of the particular terminal device which may be employed in circuit with the paired units. That is to say, while a common and easily understandable example of a ferrite switch embodying the present invention is a four-port switch having paired, mutually orthogonal rectangular ports at each terminus and a series pair of Faraday rotators interconnecting such terminal devices, the invention is not limited to a specific number of ports.

Further, the invention is applicable to waveguides of both circular and rectangular cross section, with the magnetic fields that are appropriate therefor. Also, as will be explained herein, the invention is pertinent to devices employing branched parallel circuits as well as to single series circuits, irrespective of whether all parallel branches include ferrite devices.

With the above objects and considerations in mind, the invention itself will now be described in connection with a preferred embodiment thereof given by Way of example and not of limitation, and with reference to the accompanying drawings, in which:

FIG. 1 is a vertical elevation view, partially schematic in form, showing a Faraday rotator in accordance with the present invention, portions being broken away for clarity;

FIG. 2 is a sectional view taken on line 2-2 in FIG. 1;

FIG. 3 is a perspective view, partially in schematic form, of a four-port microwave ferrite switch in accordance with the present invention, employing Faraday rotation;

FIG. 4 is a perspective view, partially schematic in form, of a four-port microwave ferrite switch in accordance with the present invention, employing electrical phase shift;

FIG. 5 is a vertical section taken from line 5-5 in FIG. 4;

FIG. 6 is a schematic diagram of one form of a fourport microwave ferrite switch of the type shown in FIG. 4; and

FIG. 7 is a schematic diagram of another four-port microwave ferrite switch similar to that of FIG. 6.

Referring now to FIG. 1, a Faraday rotator device in accordance with the present invention is indicated generally at 10. The rotator device 10 comprises a length of cylindrical waveguide 12, a pair of ferrite insert members 14 and 16 supported in substantial axial alignment within waveguide 12 by means of respective cylindrical support members 18 and 20 which may be tapered, if desired, and which are substantially transparent to microwave energy propagated through waveguide 12. Ferrite insert member 16 has a longitudinal magnetic field applied thereto by means of a solenoid 22 which is mounted on waveguide 12 at a position substantially corresponding to that of ferrite member 16 along the length of the waveguide. Solenoid 22 is energized by a fixed voltage source 24, and the magnetization of ferrite member 16 is therefore fixed at a constant selected level. Ferrite insert member 14 is subjected to a variable longitudinal magnetic field produced by a solenoid 26 which is mounted on waveguide 12 at substantially the same longitudinal position occupied by ferrite insert member 14. Solenoid 26 is connected to a voltage source 28 by means of a polarity reversing switch 30. Operation of switch 30 from one position to another causes a reversal of the polarity of the voltage applied to solenoid 26, along with a corresponding reversal of the polarity or sense of the magnetic field produced thereby in substantial longitudinal alignment with ferrite insert 14. Where it is desired, the circuits associated with voltage sources 24 and 28 may include respective impedances 32 and 34, which impedances may be made variable as a means for setting up a desired maximum degree of energization for the respective solenoids and ferrite members.

In the operation of the Farady rotator 10 in FIG. 1, and with additional reference to the sectional showing of FIG. 2, let it be assumed that the ferrite member 16 effects a 45 degree clockwise (in FIG. 2) rotation in the electrical vector of a microwave signal propagated therethrough when it is energized by voltage source 24 as shown in FIG. 1. The variable parameters associated with ferrite member 14 are in such relationship that with switch 30 in one position the ferrite member 14 also produces a 45 degress clockwise (-in FIG. 2) rotation of the electrical vector of a microwave signal presented thereto. Upon reversal ofthe position of switch 30', the sense of energization of ferrite member 14 is reversed, and a microwave signal presented thereto will experience a 45 degree counterclockwise (in FIG. 2) Faraday rotation as a result. Taking the dot-dash lines 36 as a fiducial orientation, the fixed Faraday rotation provided by ferrite member 16 is represented by the displacement of vector 38 from fiducial line 36. With switch 30 in a first position, ferrite member 14 is magnetically energized in a first sense to rotate a microwave signal presented thereto through 45 degrees in a counter clockwise (in FIG. 2) direction from fiducial line 36, as represented by vector 40.

In order to demonstrate the reciprocal nature of microwave signal propagation in rotator device 10, let it be assumed that a microwave signal is introduced into waveguide 12 at the left-hand end, as seen in FIG. 1, with its electrical vector in vertical alignment with fiducial line 36.. Upon propagation of this signal past ferrite member 14, and assuming switch 30 to be in the first position and thereby providing Faraday rotation in a sense opposite to that provided by ferrite member 16, the electrical vector of the assumed input signal will first be rotated counterclockwise (in FIG. 2) through a 45-degree displacement and then clockwise through a 45-degree displacement, with the signal output at the right-hand end of waveguide 12-liaving an electrical vector in the same orientation as that of the input signal. As is evident, if this same assumed microwave signal had been applied to the right-hand end of waveguide 12, as seen in FIG. 1, with its electrical vector in vertical alignment with fiducial line 36, and assuming switch 30 still to be in the first position, such electrical vector will be rotated first clockwise (in FIG. 2) and then counterclockwise through equal displacements of 45 degrees, and the electrical vector of the output signal at the left-hand end of waveguide 12 will again be in vertical alignment with fiducial line 36. These relationships satisfy the definition of reciprocal, and the Earady rotator of FIGS. 1, 2 and 3 is reciprocal withrespect to the assumed first position of switch 30.

Assuming now a second condition, viz., where switch 30 is in its second position, ferrite members 14 and 16 cause Faraday rotation in the same direction, rather than in opposite directions. Again assuming a microwave input signal having an electrical vector in vertical alignment with fiducial line 36 and applied to the lefthand end of waveguide 12, and with switch 30 in its second position, such electrical vector will first be rotated 45 degrees by ferrite member 14 to a position corresponding to that of vector 38, and will then be rotated through an additional 45 degrees by ferrite member 16 to a position corresponding to that of vector 42. If this output signal represented by the vector 42 were to be propagated back through the waveguide 12 toward the left-hand end as seen in FIG. 1, it would be subjected to two additional 45-degree displacements in the same direction as before, being presented as an output signal of the same orientation but opposite sign with respect to the original input signal at this end. This condition also satisfies the definition of reciprocal as intended herein, since at either end of waveguide 12 a signal having a vector orientation corresponding to vector 42 will be propagated in one port connected thereto, while a signal having a vector orientation corresponding to the direction of fiducial line 36 will be propagated in another and mutually orthogonal port. This will be better understood in connection with the description of FIG. 3.

Referring now to FIG. 3, the Faraday rot-ator is shown in connection with a pair of two-mode transducers 44 and 46, the combination comprising a four-port microwave ferrite switch. As is understood by those skilled in this art, the two-mode transducers 44 and 46 serve as transitions between the circular waveguide 12 of Faraday rot-ator 10 and the rectangular waveguide which is commonly employed in most present-day microwave circuits. Another and more important characteristic of the members 44 and 46 is their ability to distinguish between microwave signals of mutually orthogonal electrical vector orientations. For example, a microwave signal presented by waveguide 12. to member 46 in a vertical electrical vector orientation willbe propagated through rectangular port48, and none of such signal will be presented at rectangular port 50. Oorrespondingly, a microwave signal presented to transducer 46 by rotator *ltland having a horizontal electrical vector orientation will be propagated through port '50, and not through port '48. Similar selective propagation obtains in transducer 44=wi=th respect to rectangular ports 52 and 54.

In the operation of the four-port microwave ferrite switch of-FIG. 3, and assuming that switch 30 is in a first position corresponding to the first position discussed inconnection with FIG. 1, the two ferrite. insert members, 14 and 16 will produce equal and opposite rotationsof a microwave signal propagated 'therethrough, and a signal having a vertical electrical vector and being propagated: through port 52 will-be presented as an outputatport 48, the vector still being vertical. Conversely, a vertical oriented signal presented to port 48.will be transmitted through the switch to the port 52, with the vertical orienta-' :tion remaining intact. Assuming now thatswitch 30in FIG. 3 is in its second position (as discussed in connectionwithFIG. 1), (the Faraday rotation effected by the. twofern'te members 14 and 16. will now be in the same. direction. With switch 30 in this second position, the. microwave signal presented to port 52 and having a vertical electrical vector will have such vector rotated clockwise through. two cumulative 45 degree displacements and will be presented to the transducer 46 as a signal having a horizo-ntal' electricalvector. Such signal will appear as an output signal at port 50, and no output will be, presented at port 48. Conversely, if this output signal at port 50 wereto be applied as an input signal at such port, such signal would be subjected to two cumulative clockwise (inFIG. 2) 45-degree displacements before being presented to member 44 as a microwave signal having a vertical (and downwardly directed) electrical vector. As is evident, such a microwave signal will be presented as an output signal at port .52, and no output will appear at port ,54. The reciprocal relationship is thus demon strated with respect tosignal input at port 52,-and for either position of switch 30; similar analysis will show corresponding reciprocal relationship with respect to input signals applied to each of the other ports. As previi ously stated the present invention is not limited to a particular form ofwaveguide structure. FIGS. 1 through 3, show an exemplary embodiment in connection with a waveguide having a circular cross section, whereas FIGS. 4 and 5 are exemplaryof an embodiment of the present invention as applied to waveguide structure having a rec: tang-ular cross section. In addition, and as previously stated, the invention is not limited to theutilization of Faraday rotation in order to achieve the desired results, such results also being obtainable through microwave ferrite phase shift devices. The embodiments of FIGS, 1 through, 3 are exemplary of the Faraday rotation ap-. plication, while FIGS. 4 through 7 pertain to the use of electricalv phase shift.

Referring now to FIG. 4, a reciprocal microwave ferrite electrical phase shift device analogous to the Fara? day rotation device 10 of the earlier figures is indicated generally at 56, such device comprising a pair of nonreciprocal ferrite units 58 and 60. Ferrite unit 58 is subjected to a fixed energization by means of a permanent magnet 62 which applies a tranverse magnetic field to a pair of ferrite insert members 64,,and 66 (see FIG. 5) mounted within the unit 58. As may clearly be seen in FIG. 5, permanent magnet 62 is C-shaped in cross section and provides atransverse magnetic field in one side of the divided waveguide which comprises the case, or main aoeaeve structures of ferrite unit 58. It will be understood that permanent magnet 62 could be replaced by a similarlyshaped piece of magnetizable material having an electrical coil wound thereon and connected to a source of fixed electrical potential, as in the manner of solenoid 22 of FIG. 1. Alternatively, the solenoid 22 of FIG. 1 could be replaced by a cylindrical permanent magnet around waveguide 12. As may be seen in FIG. 5, the wave-propagating chamber 68 of unit 58 comprises one phase-changing unit including the ferrite slabs 64 and 66. Wave-propagating chamber 70, on the other hand, contains no ferrite members and therefore serves as an ordinary hollow waveguide structure.

The cross-section of ferrite unit 60 of FIG. 4 is identical to that of unit 58 shown in FIG. 5, with the exception that the magnet 72 is an electromagnet having a coil 74 connected to a source of electrical potential 76 through a polarity reversing switch 78. In a manner analogous to that of the use of resistor 34 in FIG. 1, a resistor 80 may be included in the circuit with potential source 76 in FIG. 4.

The non-reciprocal ferrite units 58 and 60 are connected in series relationship between a pair of terminal members shown in FIG. 4 as folded Magic Tee devices 82 and 84, the former including rectangular ports 86 and 88, and the latter including rectangular ports 90 and 92.

The operation of FIG. 4 will now be described in connection with FIG. 6, the latter comprising an exemplary circuit diagram of the structure of FIG. 4. A microwave signal introduced into port 86 with a vertical electrical vector will be divided in equal phase in the two branches 94 and 96. The block 98 represents the fixed ferrite phase shift section or chamber of unit 58 of FIG. 4, and the block 100 represents the variable or switchable ferrite section or chamber of unit 60 of FIG. 4. The arrows and associated arabic numbers in blocks 98 and 100 indicate the relative degree of electrical phase shift to which a microwave signal is subjected in passing therethrough in the direction of propagation indicated by the arrow, and the two sets of arrows grouped as I and II represent the different relative phase shift conditions that obtain in the variable phase shift device as between the diiferent positions of switch 78 of FIG. 4.

A vertically polarized microwave signal having been presented to port 86, the signal divides into two components of similar phase in branches 94 and 96 of folded Magic Tee 82. The signal in branch 94 passes through block 98 with no phase shift and through block 100, assuming switch 78 to be in a first condition identified by I, with a phase shift of 180 degrees. The signals in branches 102 and 104 of folded Magic Tee 84 are thus 180 degrees out of phase, and, in the manner well known in connection with folded Magic Tee devices, an output signal is presented at port 90. Conversely, if such output signal at port 90 were to be applied thereto as an input signal, components of such signal would appear in branches 102 and 104 in phase opposition. Assuming switch 78 still to be in condition I, the signal in branch 102 passes through block 100 with zero phase shift and through block 98 with 180 degrees phase shift to be presented .in branch 94 of Magic Tee 82 in phase coincidence with the component in branch 96, whereupon an output is presented at port 86. The reciprocal relationship is thus demonstrated with respect to an input to port 86 for condition I of switch 78.

Assuming switch 78 to be in the position corresponding to II in block 100, and again applying a vertically polarized signal to port 86, such input signal is again separated into two in-phase components in branches 94 and 96. The component in branch 94 experiences zero phase shift in passing through block 98 and in passing through block 100, so that it arrives at branch 102 in phase coincidence with the signal in branch 104, and an output signal appears at port 92. Conversely, if such output signal at port 92 were applied thereto as an input signal, such input signal would be divided into two in-phase components in branches 102 and 104. The component in branch 102 would be subjected to two cumulative phase shifts of 180 degrees each in passing through blocks and 98, assuming switch 78 still to be in the position corresponding to condition II. The components thus presented in branches 94 and 96 are again in phase coincidence, and an output signal appears at port 86. The reciprocal nature of the device of FIGS. 4, 5 and 6 is thus established for either condition of switch 78 where an input is applied to port 86. Similar analysis will demonstrate the reciprocal relationship with respect to inputs applied to each of the other ports 88, 90 and 92. It will be noted that the device of FIG. 6 is reciprocal as to phase relationships between signals propagated in opposite directions therein, in addition to the reciprocal relationship that obtains with respect to propagation between the several ports.

FIG. 7 shows in block diagram a circuit analogous to that of FIG. 6, but including paired fixed and variable ferrite phase shift devices in each of the two waveguide structures extending between the two Magic Tee devices. The legends employed in FIG. 7 are substantially identical to those in FIG. 6, except for the fact that each phase shift unit produces a relative shift of but 90 degrees instead of the 180 degrees encountered in FIG. 6.

In the operation of the circuit shown in FIG. 7, it may be shown in a manner similar to that employed in connection with the discussion of FIG. 6 that a vertically polarized input signal at port 106 will divide into in-phase components in branches 108 and 110. Assuming the associated electrical switch to be in the position corresponding to the condition indicated by I, the signal in branch 108 passes through blocks 112 and 114 with zero phase shift, while the component in branch passes through blocks 116 and 118 with a cumulative phase shift of 180 degrees. The resulting signals in branches 120 and 122 are in phase opposition, and an output signal appears at port 124. A converse analysis shows the reciprocal relationship with respect to this input signal at port 106 irrespective of the switch conditions I and II. Similarly, reciprocal transmission may be demonstrated for input signals applied to ports 124, 126 and 128, irrespective of the switch conditions I and II.

As different needs arise, other applications of the basic concept of this invention will suggest themselves to those skilled in the art. In addition, it should be noted that the invention described in connection with FIGS. 4 through 7 is not limited to the use of the folded Magic Tee shown therein, since other suitable four-port hybrid junctions (such as a short-slot, side wall coupler) may be employed instead. Hence, the invention is not to be considered as limited to the particular details given, nor to the specific application to which reference has been made during the description of the device except insofar as may be required by the scope of the appended claims.

What is claimed is:

1. A reciprocal microwave device comprising a plurality of terminals connected to each end of said device, means for the transmission of energy between said terminals, and means for providing the reciprocal transmission of energy between said terminals comprising a plurality of non-reciprocal means connected in series between said terminals, at least one of said non-reciprocal means impar-ting a reversible substantially 45-degree polarity rotation to the transmission of energy in either of two oppositely selected senses.

2. A switching device, comprising first ferrite means for altering substantially 45 degrees in a selected sensea characteristic of an electromagnetic signal propagated therethrough, second ferrite means for altering substantially 45 degrees in either of two oppositely disposed selected senses such characteristic of said electromagnetic signal propagated therethrough, and first and second terminals each adapted to accommodate a plurality of waveguide port means, and means for providing a reciprocal relationship between said first and second terminals comprising means for connecting said first and second signal a1- tering means in a series relationship between said first and second terminals.

3. A microwave switching device, comprising ferrite means for rotating about 45 degrees in a selected sense the electrical phase of a microwave signal propagated therethrough, ferrite means for rotating about 45 degrees in either of two oppositely disposed selected senses the electrical phase of a microwave signal propagated therethrough, and first and second terminal means each adapted to accommodate a plurality of waveguide port means and means for providing a reciprocal signal relationship between said two terminal means comprising means for connecting said two rotating means in a series relationship between said two terminal means.

4. A reciprocal microwave switching device, comprising a first ferrite means for rotating substantially 45 degrees in either of two selected senses the orientation of the electrical vector of a microwave signal propagated therethrough, a second ferrite means for rotating substantially 45 degrees in a selected sense the orientation of the electrical vector of a microwave signal propagated therethrough, and first and second terminal means each adapted to accommodate a plurality of waveguide port means, and means for providing a reciprocal signal rela tionship between said two terminal means comprising means for connecting said two rotating means in a series relationship between said two terminal means.

5. A microwave switching device, comprising a circular waveguide means for propagating microwave energy, said waveguide means connected between terminal means, said terminal means adapted to accommodate a plurality of waveguide port means, first and second ferromagnetic insert members positioned in substantial alignment in the direction :of propagation within said waveguide means, means for imparting substantially a 45-degree polarity rotation to incident microwave energy in either of two oppositely disposed senses comprising means for energizing said first ferromagnetic member in either of two opposite magnetic polarities, means for imparting substantially a 45-degree polarity rotation to incident microwave energy in a selected sense comprising means for energizing said second ferromagnetic member inone of such magnetic polarities, branch circuit means comprising a plurality of waveguide port means connected to said waveguide means, and means for providing a reciprocal energy relationship between selective terminal and branch port means comprising means for the selective energization of said first ferromagnetic member in either of two opposite polarities.

6. A microwave rotator device comprising circular waveguide means for propagating microwave energy, said waveguide means connected between first and second terminals attached to accommodate a plurality of waveguide port means, first and second ferromagnetic insert members positioned in substantial alignment in the direction of propagation within said waveguide means, each of said 10 insert members attached to impart substantially in 45- degree polarity rotation of incident microwave energy in response to magnetic energization of such member, means for energizing said first ferromagnetic member in either of two opposite magnetic polarities, means for energizing said second ferromagnetic member in one of such magnetic polarities to provide a reciprocal relationship in the transmission of microwave signals in said waveguide means in opposite directions between said waveguide port means, wherein said means for energizing said first member includes a voltage source, electromagnetic means connected to said first voltage source for establishing a magnetic field through said first inserted member parallel to the direction of propagation of microwave energy in said waveguide means, and means for reversing the electrical polarity of the voltage applied to said electromagnetic means by said voltage source.

7. A microwave rotator device comprising circular waveguide means for propagating microwave energy, said waveguide means connected between first and second terminals, both of said terminals adapted to accommodate a plurality of waveguide port means, first and second ferromagnetic insert members positioned in substantial alignment in the direction of propagation within said waveguide means, each of said inserted members attached to impart substantially a 45-degree polarity rotation of incident microwave energy in response to magnetic energization of such member, means for energizing said first ferromagnetic member in either of two opposite magnetic polarities, means for energizing said second ferromagnetic member in one of such magnetic polarities to provide a reciprocal relationship in the transmission of microwave signals in said waveguide means in opposite directions between said waveguide port means, wherein said means for energizing said first member includes electromagnetic means for establishing a magnetic field through said first insert member parallel to the direction of propagation of microwave energy in said waveguide means, and means for selectively applying voltages of alternating opposite polarity to said electromagnetic means.

References Cited in the file of this patent UNITED STATES PATENTS lied on).

Turner: IRE Transaction on Microwave Theory and Techniques, July 1958, page 300.

Scharfman: Proceedings of the IRE, October 1956, page 1457. 

1. A RECIPROCAL MICROWAVE DEVICE COMPRISING A PLURALITY OF TERMINALS CONNECTED TO EACH END OF SAID DEVICE, MEANS FOR THE TRANSMISSION OF ENERGY BETWEEN SAID TERMINALS, AND MEANS FOR PROVIDING THE RECIPROCAL TRANSMISSION OF ENERGY BETWEEN SAID TERMINALS COMPRISING A PLURALITY OF NON-RECIPROCAL MEANS CONNECTED IN SERIES BETWEEN SAID TERMINALS, AT LEAST ONE OF SAID NON-RECIPROCAL MEANS IMPARTING A REVERSIBLE SUBSTANTIALLY 45-DEGREE POLARITY ROTATION TO THE TRANSMISSION OF ENERGY IN EITHER OF TWO OPPOSITELY SELECTED SENSES. 